It looks like you calculated the circumference of the wheel incorrectly.
You say it is a 72.5 mm wheel. I assume that that is the diameter.
72.5 * 3.1416 = 227.766
So, the circumference is not 217 mm; it is closer to 227 mm.
duration4 = duration1 + duration2 + duration3;
duration = duration3/3;
vitesse = (217/(duration)*3.6); //217 = circonférence de la roue en mm
I think you made mistakes in your calculation of "duration" and "vitesse".
You also say that your two 7-segment displays use 14 inputs. Unless you go faster than 69 km/h, you only need 13 inputs. (The digit on the left only needs 6 inputs, not 7. See the picture.)
